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>>that planet's orbit (i.e. the ecliptic about the other star) must be in the same plane as Earth.<< (No, the plane only has to point towards us from any direc
by deletes 13y ago
>>that planet's orbit (i.e. the ecliptic about the other star) must be in the same plane as Earth.<<
(No, the plane only has to point towards us from any direction, it doesn't have to be on the same plane as earth.)
EDIT: I didn't see it from the other perspective. :(
- mnw21cam 13y agoThat's what that means. The Earth has to be on the plane on which their ecliptic sits. However, yes, our ecliptic needn't align with theirs.
- ISL 13y agoUnless you add the requirement that they be able to detect us when Earth eclipses the Sun from their perspective.
- deletes 13y agoOnly now I understand your point. Of course both planet must be able to detect each other, as radio transmissions must be focused to be able to travel the distance and be detected with non-science-fiction telescopes.
- mnw21cam 13y agoIndeed. For two-way detection, the two ecliptics must be in the same plane. Or more accurately, the two ecliptics must be close enough to a common plane, where the common plane passes through both planets and "close enough" means within half a degree on Earth's side.